Biodesulfurization of hydrocarbons

ABSTRACT

A process for treating liquid hydrocarbon, includes the steps of providing a liquid hydrocarbon containing complex sulfur-containing compounds, providing a bioactive material selected from or derived from members of genus Alcaligenes; and exposing the liquid hydrocarbon to the bioactive material under effective conditions such that the bioactive material interacts with the complex sulfur compounds and transforms the organic sulfur-containing compounds into inorganic sulfur compounds.

BACKGROUND OF THE INVENTION

[0001] The invention relates to biodesulfurization of hydrocarbons and,more particularly, to a bioactive material and method using same forbreaking down complex organic sulfur-containing compounds within ahydrocarbon so as to facilitate removal of same.

[0002] Sulfur content in hydrocarbons is an important concern fornumerous reasons, particularly when the hydrocarbon is to be used as afuel. Numerous methods, systems and compositions are known and used forremoval of sulfur from the hydrocarbon. Although these are somewhateffective, problems remain.

[0003] Sulfur is particularly difficult to effectively remove when it ispresent in organic sulfur-containing compounds, such asdibenzothiophene. The normal degradative pathway for dibenzothiophene(DBT) results in a different, but still complex organicsulfur-containing compound, such as 3-hydroxy-2-formilbenzothiophene,and removal of this compound undesirably removes carbon from thehydrocarbon.

[0004] In light of the foregoing, it is clear that the need remains foraddressing the removal of sulfur when present in complex organiccompounds.

[0005] It is therefore the primary object of the present invention toprovide a method and bioactive material which are well suited to thisremoval.

[0006] It is a further object of the present invention to provide amethod and bioactive material which are useful for reducing the C15+fraction of a hydrocarbon, and thereby further improving thecharacteristics of same.

[0007] Other objects and advantages of the present invention will appearhereinbelow.

SUMMARY OF THE INVENTION

[0008] In accordance with the present invention, a process is providedfor treating liquid hydrocarbon, which process comprises the steps ofproviding a liquid hydrocarbon containing organic sulfur-containingcompounds; providing a bioactive material selected from or derived frommembers of genus Alcaligenes; and exposing said liquid hydrocarbon tosaid bioactive material under effective conditions such that saidbioactive material interacts with said organic sulfur-containingcompounds and transforms said organic sulfur-containing compounds intoinorganic sulfur compounds. These inorganic sulfur compounds can then bemore easily separated from the hydrocarbon.

[0009] A bioactive material is also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A detailed description of preferred embodiments of the presentinvention follows, with reference to the attached drawings, wherein:

[0011]FIG. 1 schematically illustrates a selective pathway of DBTbreakdown when treated in accordance with the invention, as well as aconventional degradative pathway;

[0012]FIG. 2 illustrates activity and percent reduction in DBT as afunction of pH in accordance with the present invention;

[0013]FIG. 3 illustrates activity over a range of temperatures inaccordance with the present invention;

[0014]FIG. 4 illustrates activity as a function of concentration of asubstrate in accordance with the present invention;

[0015]FIG. 5 illustrates activity as a function of concentration of thebioactive material;

[0016]FIG. 6 illustrates data for a hydrocarbon before and aftertreatment to show the presence in the product of biphenyl;

[0017]FIG. 7 shows bioactivity of the bioactive material of the presentinvention in connection with other organic sulfur compounds;

[0018]FIG. 8 shows excellent results obtained in treating a hydrocarbonin terms of reduction in organic sulfur compounds, as well as reductionin the C16+ fraction; and

[0019]FIG. 9 shows sulfur removal results in connection with emulsionshaving different ratios of hydrocarbon to water.

DETAILED DESCRIPTION

[0020] The invention relates to a bioactive material and a method orprocess for using same in treating hydrocarbons to transform complexorganic sulfur compounds into more easily removable inorganic sulfurcompounds, thereby making sulfur removal easier.

[0021] In accordance with the present invention, it has been found thatmembers of the genus Alcaligenes, under certain conditions, haveexcellent activity toward attacking carbon-sulfur-carbon bonds incomplex organic sulfur-containing compounds, thereby leading toinorganic sulfur compounds as desired. The species Alcaligenesxyloxidans has been found to be particularly effective at this selectivetransformation. Cells of this material have been deposited with asuitable facility, and an identification from this facility isforthcoming.

[0022] The bioactive material of the present invention preferablyincludes cells from Alcaligenes xyloxidans strains and more specificallyan enzymatic extract from the active cells which extract isbiocatalytically active on organic sulfur compounds as described above.This extract contains an oxidase enzyme believed to be particularlyactive.

[0023] In accordance with the present invention, the bioactive materialas described above is advantageously used to transform organicsulfur-containing compounds contained in hydrocarbons into inorganicsulfur compounds, which are more readily removed from the hydrocarbon.Further, these inorganic compounds have an affinity toward water and,when the treatment process is carried out with an emulsion, theinorganic sulfur compounds are formed in or travel to the water phasefurther facilitating separation. Still further, this separation ofsulfur is accomplished without removal of desirable constituents fromthe hydrocarbon.

[0024] Typical hydrocarbons which can advantageously be treated inaccordance with the present invention include any liquid hydrocarbon orhydrocarbon slurry which contains organic sulfur compounds. Preferredhydrocarbons for such treatment include, among others, bitumen, heavycrude, medium crude, Diesel fuel, gasoline, coal slurry and mixturesthereof. Bitumen is particularly advantageously treated in accordancewith the present invention since this hydrocarbon contains significantamounts of organic sulfur-containing compounds.

[0025] In accordance with the present invention, it has further beenfound that some strains of the bioactive material in accordance with thepresent invention are hydrophilic and lipophobic. As the mechanism iscarried out by contacting the materials, this makes contacting of thebioactive material with hydrocarbon difficult. In accordance with thepresent invention, this problem is solved, when present, by forming ahydrocarbon in water emulsion of the hydrocarbon, and adding thebioactive material to the water, either before or after emulsionformation, such that the bioactive material is nevertheless in intimatecontact with a major portion of the hydrocarbon.

[0026] As set forth above, the bioactive material in accordance with thepresent invention is particularly effective in attackingcarbon-sulfur-carbon bonds of complex organic sulfur-containingcompounds. For example, and as shown in FIG. 1, dibenzothiophene (DBT),when exposed to the bioactive material in accordance with the presentinvention, reacts along a selective pathway wherein the end result is afinal product including biphenyl and inorganic sulfur compounds such assulphates, hydrogen sulfide and the like. These inorganicsulfur-containing compounds are more readily separated from thehydrocarbon using conventional methods and equipment. Thus, inaccordance with the present invention, the bioactive material providesactivity along selective pathways which advantageously render sulfur inthe hydrocarbon more easily removable.

[0027]FIG. 1 also illustrates, in the right hand portion of the figure,the degradative pathway experienced without a selective catalyst such asthe bioactive material of the present invention. As shown, DBT may breakdown but this does not result in sulfur being moved to inorganic, lesscomplex, and more easily removable compounds.

[0028] The bioactive material in accordance with the present inventionis also active in breaking down other organic sulfur-containingcompounds, such as alkylthiophenes, naphthobenzothiophene,dimethylthiopene, thionaphthene and the like. The mechanism of thebioactive material in accordance with the present inventionadvantageously allows for selective breaking down of such compounds, andany other compounds involving carbon-sulfur-carbon bonds, so as totransform the sulfur into inorganic sulfur compound form as desired.

[0029] The bioactive material and hydrocarbon in accordance with thepresent invention are advantageously exposed to each other, preferablyat a concentration of at least about 1 mg/ml of total protein in theextract per ml of hydrocarbon of total emulsion, more preferably betweenabout 1 mg/ml and about 5 mg/ml of total protein in the extract or ml ofhydrocarbon of total emulsion, and at effective conditions, preferably atemperature between about 30° C. and about 50° C. and a pH of betweenabout 7.0 and about 8.0, such that the complex sulfur-containing organiccompounds are transformed as desired.

[0030] Conversion rates of dibenzothiophene, in accordance with thepresent invention, are advantageously at least about 70% wt., whichresults in a substantially facilitated sulfur removal from thehydrocarbon as desired. This advantageously transforms a substantialamount of DBT and other difficult-to-remove sulfur into more easilyremoved form, and further into a form which does not include carbon thatis preferably left in the hydrocarbon.

[0031] The bioactive material was isolated from a soil and hydrocarbonsample which is typical of a local environment in Venezuela. A sample ofthis soil was then mixed with a mineral medium and dibenzothiophene soas to obtain a biomass from which the bacteria can be isolated.Utilizing known isolation techniques, this leads to identification ofthe genus and species. From this, a pure culture can be obtained andsubjected to biochemical tests that confirm Alcaligenes, and further canbe subjected to DNA testing which confirm xyloxidans as the species.

[0032] From a pure culture of the material, biomass is further producedand subjected to centrifuge so as to separate cells which can beprocessed, for example using mechanical or other extraction methods, toobtain an enzymatic extract containing oxidase and possessing theactivity discovered in accordance with the present invention. Usingknown methods, an inoculum is obtained from which a biomass is produced,and the desired extract is obtained from the biomass as more fullydescribed below.

[0033] A process for extracting the particularly desirable enzymaticextract in accordance with the present invention can be conducted byfirst sterilizing a culture medium in a suitable vessel, for example ata pressure of 15 psi for 15 minutes at a temperature of 121° C.

[0034] The vessel is then preferably held at a fermentation temperature,preferably of about 30° C., and ventilated or exposed to a flow of airfor about 1 hour, with air flow rate at the rate of about 1 liters perminute.

[0035] The vessel is preferably inoculated with the strain, for examplein an amount of about 0.2% weight of the culture medium. The bacteria isthen preferably allowed to incubate, for example at a temperature of 30°C., with agitation at 150 rpm, for a period of about 72 hours, and in amineral medium containing organic sulfur, for example DBT, as the solesource of sulfur, and further with a glucose as a growth factor, forexample in an amount of about 0.2% wt.

[0036] The material is then subjected to an incubation period forapproximately 18-24 hours, without agitation, and with a flow of airpreferably of about 2 liters per minute, and a temperature of about 30°C.

[0037] The incubated material is then advantageously subjected tocentrifugation, for example at 10,000 x g, for about 20 minutes, so asto recover the biomass material and separate material from which theextract is to be obtained.

[0038] This separated material is then re-suspended in a buffer solutionof potassium phosphate (100 mM), having a pH of 7, and this suspensionis subjected to a Braun homogenizer so as to rupture the cells.

[0039] The solution is then again subjected to centrifuge at 10,000×g,for an additional period of about 20 minutes, and supernatant materialcontaining the desired enzymatic extract can the be withdrawn from thesolution.

[0040] The following examples further demonstrate the bioactive materialand use same in accordance with the present invention.

EXAMPLE 1

[0041] In this example, an enzymatic extract of Alcaligenes xyloxidansidentified as INTS-1 was prepared in mixture with a hydrocarbon, withthe pH varied between 7, 8 and 9, and the activity of the bioactivematerial was measured.

[0042]FIG. 2 shows activity for INTS-1 at various pH, along with percentreduction in DBT.

[0043] As shown, best results are obtained at pH greater than 6 and upto 9.

[0044] The bioactive material was then further evaluated, at pH of 7,and at temperatures between 30° C. and 50° C. FIG. 3 shows the resultsof this testing, and it can be seen that the material was effectivebetween temperatures of 30° C. and 50° C.

[0045] Activity of the strain as identified above was then measured fora fixed concentration of the enzymatic extract relative to increasingamounts of DBT substrate. FIG. 4 shows the results obtained, and thecontinuous increase in activity shows that saturation by the DBTsubstrate occurs at a value greater than 100 ppm.

[0046] Activity of the bioactive material as described above was thenevaluated at different concentrations of an enzymatic extract per volumeof hydrocarbon. FIG. 5 shows the results of this evaluation, and showsthat activity of the material increases gradually above a concentrationof 2 mg/ml. An optimum concentration of this strain is about 2 mg/mldepending upon whether the additional activity obtained at higherconcentration is cost justified.

EXAMPLE 2

[0047] In this example, a hydrocarbon sample was obtained whichcontained dibenzothiophene (DBT), and was exposed to bioactive materialin accordance with the present invention.

[0048]FIG. 6 sets forth gas chromatography—mass spectrometry data forthe starting product and finishing materials for two runs, namely“Experimental 1” and “Experimental 2”, and a “Control” which containedno bioactive material. As set forth above, the catalytic activity of thebioactive material in accordance with the present invention breaks downDBT to form biphenyl (BF) as well as the desired inorganic sulfurcompounds which are more readily removed. The second and third patternsshown in FIG. 6 clearly show a new spike appearing which corresponds tothe identification of biphenyl (BF), thereby confirming thattransformation of dibenzothiopene to biphenyl is occurring, as desired,and this confirms transformation of sulfur from the organic compound toinorganic compounds, and also as desired.

[0049] Table 1 sets forth these results in table form as well. TABLE 1Area Relative (%) DBT BF Control 99.05 0.95 Experimental 1 92.69 7.31Experimental 2 92.62 7.38

EXAMPLE 3

[0050] In this example, the same bioactive material as evaluated inExamples 1 and 2 was further evaluated in connection with activity onother organic sulfur compounds, namely dimethylthiopene andthionaphthene. FIG. 7 shows the relationship between incubation time indays and activity in connection with these two other organic sulfurcompounds. As shown, the bioactive material in accordance with thepresent invention has activity toward breaking down these organic sulfurcompounds as well.

EXAMPLE 4

[0051] In this example, a bitumen in water emulsion was prepared havinga ratio of hydrocarbon to water of 70:30, and the hydrocarbon containedDBT, alkyl thiopenes and naphthabenzothiophene, as well as a substantialfraction of C16+ hydrocarbons.

[0052] This hydrocarbon was treated using the bioactive material of thepresent invention, and an analysis of the starting hydrocarbon and finalproduct are shown in FIG. 8. As shown, the organic sulfur compounds aresubstantially reduced, as is the C16+ fraction, all as desired inaccordance with the present invention.

EXAMPLE 5

[0053] As set forth above, the hydrocarbon to water ratio of emulsionsformed in accordance with the present invention can also effect theamount of sulfur removal.

[0054] Sulfur removal was evaluated for five different emulsions havingratios of hydrocarbon to water of between 70:30 and 30:70, and theresults of this evaluation are set forth in FIG. 9.

[0055] As shown, the percentage removal of sulfur increases as the watercontent of the emulsion increases.

[0056] In accordance with the foregoing, it is clear that a bioactivematerial, and method for using same, have been provided whichadvantageously convert dibenzothiophene and other organicsulfur-containing compounds into inorganic sulfur compounds such as SO₄compounds and H₂S, along with biphenyl hydrocarbons. This isadvantageous in that the sulfur is then more easily removable when ininorganic form, as desired in accordance with the present invention.

[0057] This invention may be embodied in other forms or carried out inother ways without departing from the spirit or essentialcharacteristics thereof. The present embodiment is therefore to beconsidered as in all respects illustrative and not restrictive, thescope of the invention being indicated by the appended claims, and allchanges which come within the meaning and range of equivalency areintended to be embraced therein.

What is claimed:
 1. A process for treating a liquid hydrocarbon,comprising the steps of: providing a liquid hydrocarbon containingorganic sulfur-containing compounds; providing a bioactive materialselected from or derived from members of genus Alcaligenes; and exposingsaid liquid hydrocarbon to said bioactive material under effectiveconditions such that said bioactive material interacts with said organicsulfur-containing compounds and transforms said organicsulfur-containing compounds into inorganic sulfur compounds.
 2. Theprocess of claim 1, wherein said bioactive material is selected from orderived from Alcaligenes xyloxidans.
 3. The process of claim 1, whereinsaid bioactive material transforms said organic sulfur-containingcompounds by breaking carbon-sulfur-carbon bonds therein.
 4. The processof claim 1, wherein said bioactive material is an enzymatic extract of amember of said genus Alcaligenes, and wherein said enzymatic extract hasselective activity on carbon-sulfur-carbon bonds in said complexsulfur-containing compounds.
 5. The process of claim 4, wherein saidenzymatic extract contains oxidase.
 6. The process of claim 1, furthercomprising the step of forming a hydrocarbon in water emulsion of saidliquid hydrocarbon and wherein said exposing step comprises exposingsaid emulsion to said bioactive material.
 7. The process of claim 6,wherein said step of forming said hydrocarbon in water emulsioncomprises forming said emulsion having a ratio by weight of hydrocarbonto water at least about 70:30.
 8. The process of claim 6, wherein saidstep of forming said hydrocarbon in water emulsion comprises formingsaid emulsion having a ratio by weight of hydrocarbon to water betweenabout 70:30 and about 30:70.
 9. The process of claim 6, wherein saidstep of providing said bioactive material comprises providing a waterphase for said emulsion which contains said bioactive material, andwherein said step of forming said emulsion exposes said liquidhydrocarbon to said bioactive material.
 10. The process of claim 6,wherein said inorganic sulfur compounds are present in said water phase.11. The process of claim 1, wherein said liquid hydrocarbon is selectedfrom the group consisting of bitumen, heavy crude, medium crude, Dieselfuel, gasoline, coal slurry and mixtures thereof.
 12. The process ofclaim 1, wherein said liquid hydrocarbon is bitumen.
 13. The process ofclaim 1, wherein said organic sulfur compounds include dibenzothiophene,and wherein said inorganic sulfur compounds include sulphates, hydrogensulfide and mixtures thereof.
 14. The process of claim 1, furthercomprising the step of separating said inorganic sulfur compounds fromsaid liquid hydrocarbon.
 15. The process of claim 1, wherein said liquidhydrocarbon further comprises a C15+ fraction, and wherein said exposingstep reduces said C15+ fraction.
 16. The process of claim 1, whereinsaid effective conditions include a temperature between 30° C. and 50°C. and a pH between 7.0 and 8.0.
 17. A bioactive material of theAlcaligenes genus and xyloxidans species, which is effective, at atemperature between 30° C. and 50° C. and a pH between 7.0 and 8.0, inbreaking down carbon-sulfur-carbon bonds in organic sulfur-containingcompounds.